A fuel injection device is generally known in the art, which is composed of a control body having a pressure control chamber, and a valve member for opening and closing a valve portion in accordance with fuel pressure in the pressure control chamber. According to the fuel injection device of this kind, a fuel inlet port is opened to the pressure control chamber of the control body so that the fuel from the fuel supply line flows into the pressure control chamber, and a fuel outlet port is likewise opened to the pressure control chamber so that the fuel is discharged from the pressure control chamber to the fuel return line. Communication and non-communication (block-off of the communication) between the fuel outlet port and the fuel return line is controlled by a pressure control valve so that the fuel pressure in the pressure control chamber is controlled.
According to a known fuel injection device, for example, as disclosed in Japanese Patent Publication No. H6-108948 or Japanese Patent No. 4054621, the fuel injection device further has a floating member movable in the pressure control chamber. The floating member has a press-contacting surface, which is opposed in an axial direction of the floating member to a pressure control surface exposed to the pressure control chamber. A fuel inlet port as well as a fuel outlet port is opened at the pressure control surface. When a pressure control valve is operated to communicate the fuel outlet port with a fuel return line, the press-contacting surface of the floating member is attracted to the pressure control surface (at which the fuel outlet port is opened) by fuel flow from the pressure control chamber to the fuel outlet port. When the floating member is brought into contact with the pressure control surface, the press-contacting surface of the floating member is pressed against the pressure control surface, so that communication between the fuel inlet port and the pressure control chamber as well as communication between the fuel inlet port and the fuel outlet port is blocked off.
According to the fuel injection device of Japanese Patent No. 4054621, a surface portion of the pressure control surface (surrounding the fuel inlet port) is recessed, while another surface portion of the pressure control surface (surrounding the fuel outlet port) is not recessed but formed in a flat shape. The press-contacting surface of the floating member is also formed in a flat shape.
In the above fuel injection device, when the press-contacting surface of the floating member is pressed against the pressure control surface in order to block off the communication between the fuel injection port and the pressure control chamber, a surface area of the floating member (that is, the press-contacting surface) which is in contact with the pressure control surface is large. Therefore, it is difficult to increase surface pressure (pressing force per unit surface area). As a result, high pressure fuel from the fuel inlet port may pass through a gap between the pressure control surface and the press-contacting surface of the floating member. In other words, it is difficult to surely block off the communication between the fuel inlet port and the pressure control chamber. Therefore, when the fuel outlet port is opened (that is, when the fuel outlet port is communicated to the fuel return line), rapid pressure increase of the fuel in the pressure control chamber may not be realized, and thereby a rapid opening operation of the valve portion may not be possible.